Occasional specimens with smoothish culm or smaller achenes and scales than usual appear to approach C. houghtonii, but in each case all other characters point to C. schweinitzii. Specimens from the vicinity of Caseville, Huron Co., however, come close to C. houghtonii. Quite probably a hybrid complex is involved here, for other specimens from Huron Co. appear somewhat intermediate between C. lupulinus and C. houghtonii.